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Question DetailsAsked on 8/24/2017

Problem started with bad mildew/musty smell and I began killing/swatting these sewer/drain gnats all day everyday in every room of my apartment. The outside of my front door stayed completely covered with them on a daily basis. Maintenance found leaking pipe in crawl space below me. Pipe replaced a week later. Next 8 days sewer gnats were still OUT OF CONTROL.Last week maintenance set off pesticide bombs in crawl space and my apartment. Came home to hundreds of those dead bugs everywhere. Calmed down, now 2 days later starting to see sewer/drain gnats again, they are tiny babies in size this time. Moldy/musty/mildew smell is now really bad. It's only in my bedroom coming through wall heater. Smell gets really bad at night. Makes me sick to my stomach. Brown rust can be physically seen inside all my wall heaters. Out of no where I came home yesterday to a pile of dead "flies" all over my bedroom window ledge. HELP!! This guessing and quick fixes is not the answer to the problem.

IF you have steam or hot water baseboard heating, this sort of thing is commonly from leaking piping at the heaters or from the heater radiator itself.

It could be you have or had a sewer leak (you did not say what kind of pipe was leaking) - in which case if the crawlspace was not treated (usually with quicklime) or TOTALLY dried out (which kills the fly eggs) you might just be getting new crops of flies hatching out in the wet crawlspace.

You say smell is coming from wall heater and rust in the heaters - so I presume you mean in forced air ducts, meaning the ducts either are pulling in a lot of wet air as they passthrough the crawlspace (which would be on the "negative pressure" or return ducts in a normal forced air furnace), or if ALL ducts (supply and return both) have visible rust forming then your overall humidity is too high - which would likely be from free moisture/standing water/mud in the crawlspace - it should be totally dried out to stop the fly cycle. There are also oil-based sprays the pest control company can spray down they which coat the free wetness (ponding or wet soil) and kill the eggs. I would guess, since rust in the ducts, that the furnace may be in the crawlspace or draws its air from there and that is where it is getting the moisture and odor, routing it directly into your unit.

One other possibility, if the leak was within the subfloor, and most likely seaxge again if you are getting the fly problem - is maybe they did not clean up and disinfect the subfloor so you have raw sewage starting to mold and form rot in there, plus nurturing the flies.

You talk about maintenance doing repair and insect bombs (which only kill living insects, generally not the eggs), so I infer this is a rental situation where the building management is responsible for this sort of maintenance - so I would get on their case about getting the situation cleaned up PROPERLY.

Until that is done, you could tape over the supply vent in your bedroom - plastic sheeting with duct tape or sticky type masking tape around the perimeter, until they get it cleaned up. Reason I did not say tape the return vent too (though might turn out they will come in that way too, depending on your return filter arrangement) is if that is left open it will pull conditioned air from the rest of the house through the bedroom so it does not get too cold or hot (as the case may be).